Quotation Check – Your guide to construction quotes

A Detailed Look at Double and Single Storey Extension Costs

If you’re thinking about building an extension to your property but would like to get a handle on prices, you’ve come to the right place.

As we are sure many of you are aware; a house extension can considerably increase the value of any house, you’ll also avoid the mortgage, legal and other fees involved with moving to a new home.

But how much are builders and developers in the UK charging? What is a fair price to pay for both a single and a two-storey extension?

In 2017 we asked seven builders to provide with written quotes and estimates, below you can find an average of those prices.

You can use our research as a reference guide.

This page is all about home extensions, and we last updated it on the 21st February 2018.

How We Gathered Our Prices

As frequent visitors to our site here at Quotation Check will know, we typically source prices and estimates from various tradespeople around the country and then publish an “average” figure for those regions.

The process we use involves asking friends and family members who live in different parts of the country to get in touch with local tradespeople.

Unfortunately, because home extensions are so complicated and involve detailed communication between the homeowner, architect, builder and other tradespeople; we decided to gather only one set of quotes – which was for our property in the south of the United Kingdom.

Don’t let this put you off, our price guide can still be very valuable to those looking for a cost guide.

Our Extension Project – The Key Points

No two home extensions are identical and every project will involve different materials and techniques.

The property we refer to in our price guide below is a typical 30-year-old, 2-bed house but with enough space for a rear extension to allow for the following:

An extra double bedroom located upstairs

The remodelling of the existing space upstairs

To substantially extend and remodel the ground floor kitchen

To extend the front room to allow for extra dining space, this will involve some minor remodelling

Here is a List of What We’ve Included in Our Prices Below

Below you will find a price guide for the extension and it includes the following work:

In a nutshell, our price below includes the cost of everything involved with a two-storey extension constructed in the south of the United Kingdom, apart from the kitchen and flooring materials, which are to be supplied by the customer at additional cost.

Quotation Breakdown

Below you’ll find a chart which shows where the money is spent, this varied from company to company but we feel this is a good guide:

See All The Prices Builders Gave Us

The chart below contains all the quotes we received, we have rounded the prices to the nearest £500:

Average House Extension Cost

Below is our price guide for a two-storey house extension, the figures are an average of the prices and estimates we received from builders in 2017 and early 2018:

What About a Single Storey Extensions?

When we approached our chosen building companies for a two-storey extension price, we also enquired about the approximate cost for a single storey.

This would extend our kitchen and front room and would, of course, be less disruptive, which appealed us.

The average cost for a 4m x 5m single-storey extension came in at £33000; again this figure includes everything except the supply of the kitchen and the flooring throughout.

This price was to extend the kitchen and front room, with a tiled roof but excludes the cost of the kitchen itself (just the labour fees for its installation).

What Is “Per Metre” Pricing?

Per metre pricing is a technique used by salespeople and some builders to estimate the cost of a project by measuring the floor space and multiplying it by a figure.

We asked our chosen builders exactly how they calculate their figures and whether they use a “per square metre” calculation. Most informed us that they didn’t use a per metre system and preferred to fully customise each quote as “every house is different”.

Several of the builders suggested a starting price of £1500 per square metre for a single storey and between 40% and 60% extra for a double storey.

Again, these figures include everything except for the flooring and kitchen itself.

Extras You’ll Want to Consider

Our prices are for a typical house extension; you may end up paying more if:

You want a higher quality of finish on fittings

Large bi-folding doors or lead windows instead of typical doors/windows

Woodgrain effect Upvc windows and doors are usually more expensive than white framed products

You require an existing structure removed, perhaps a conservatory or other outbuilding

The foundations form a significant part of the house extension cost. If the ground is of a poor quality and you need extra deep foundations, that’ll cost more and should be budgeted for

Access can also affect the cost of an extension, issues may delay the completion of the project and add extra cost

Steelwork for the structural support of upper floors is expensive but the amount required is different for every house

How Your Location Affects the Price

While we only sourced quotes and prices for our property located in the south of the UK, we do have plenty of experience within the building industry as a whole.

The research we conducted suggests that while a price per metre of around £1500 for a ground level extension is typical for the South of the UK, the further away from London you live, the cheaper the cost will be.

You can, therefore, expect prices in London to be higher than the figures we have shown here.

How Long Will The Work Take?

It’s always a good idea to ask how long the work will take, some builders work alone, while others work as part of a team.

We asked all of the tradespeople to give is a rough timescale for the project.

While there were differences between each of the builders, the average time given to us was 13 weeks.

It’s worth noting that in our experience, tradespeople are often optimistic when it comes to timescales. No builder wants to suggest it will take longer substantially longer than their competitors.

Compare Extension Quotes With Rated People

We hope you found the results of our research to be insightful.

We recommend Rated People as a great place to source prices for your own project. Their website is a fantastic place to read reviews and source quotes.